Fire extinguishing composition and method of extinguishing fires



United States ...i,....,

FIRE EXTINGUISHING coMrosiTIofi METHOD OF'EXTINGUISHING FIRES Walter G. Sylvester, West Caldwell, and CharlesAnthony,

In, East Orange, N. J., assignors to Specialties Development Corporation, B'elleville, N. 1., a corporation of New Jersey I No Drawing. Application December 26, "E51, Serial No.2'63,493

2 Claims. c1. 252-7 The presentinvention relates towfire extinguishing compositions, and, more particularly, to a finely divided Accordingly, the primary object of thepresent i nven tion is to improve the fire extinguishing eifec tiveness cf dry powders comprising as a major ingredient a fire extinguishing gas evolving substance such as sodium bicarbonate and the like, and to provide such a powder which is more effective, particularly on the fires of burning highly volatile liquids, than any of the powders of this type presently commercially available.

Another object is to provide such a powder composition which can be readily projected from so-called dry powder fire extinguishing apparatus now in use.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

In accordance with the present invention, it has been discovered that the foregoing objects can be accomplished by providing a fire extinguishing powder which comprises a finely divided dry mixture of a major portion of sodium bicarbonate and the like and a minor portion of lithium carbonate.

In the preferred application of the invention, the fire extinguishing gas evolving substance is a fine particle size sodium bicarbonate capable of passing through a 150 mesh screen. The sodium bicarbonate may contain between about 0.5% and 2.5% of materials intimately admixed therewith to protect the same against moisture and to improve its free flowing characteristics. Such additive materials are well known in the art and need not be described in detail herein.

Instead of sodium bicarbonate, other so-called fire extinguishing gas evolving substances such as magnesium carbonate, potassium bicarbonate and urea or mixtures of any of these compounds including mixtures containing sodium bicarbonate may be utilized to good advantage under certain conditions. However, the use of sodium bicarbonate is preferred because of its comparative cheapness and general availability in large quantities, and its all around desirable qualities including non-hydrate forming properties, high specific heat and high heat of decomposition facilitating hea't absorption, compatibility with other powders, capability upon application of heat to decompose into suitable volumes of fire extinguishing gas and into a compound having advantageous properties similar to those of sodium bicarbonate, and desired particle size and density for projection on fires.

The lithium carbonate is intimately admixed with the sodium bicarbonate in a manner to adjust its particle size to about that of the sodium bicarbonate particles or to 2,776,942 g; Patented Jan. 8, 1957 the heat of the burning material and products of combustionito'a: value at which combustion will no longer take place,

. It has been discovered and established by trial that the addition of lithium carbonate to sodium bicarbonate provides. a composition which extinguishes fires more quickly than a 97.5% to 99.5% sodium bicarbonate composition under "similar conditions of discharge. It has also been discovered that lithium carbonate may be used in quantities'ranging from about 10% by weight to about 25% by Weight of the mixture to produce such advantage. For example, the ratio by weight of sodium bicarbonate to lithium-carbonate may be from about three to nine to one. Optimum results were obtained consistently by projecting on fires of burning volatile liquids a composition consisting essentially of by weight of sodium bicarbonate and 15% by weight of lithium carbonate. The latter quantity of lithium carbonate may be slightly in excess of the minimum quantity required to accomplish the advantages of the compositions in accordance with the present invention, but, as a practical matter, it is believed that such quantity assures more rapid extinguishing of fires under any conditions of use.

In order to demonstrate the advantages of the composition in accordance with the invention and its improved effectiveness in smothering fires, a number of one pound charges of powder compositions were placed in the powder containers of discharge apparatus of appropriate design and were pressurized to 150 pounds per square inch by introducing dry nitrogen into the containers. Each charge was tested by directing the same on a fire of burning gasoline of about one inch depth placed in a rectangular pan one foot wide and two feet long, with the discharge outlet of the extinguishing apparatus located approximately three feet from the front edge of the pan. In each instance, the gasoline, after being ignited, was permitted to burn for about fifteen seconds before discharge of the powder composition was initiated. It was noted that complete discharge of each fire extinguisher took place in about three seconds.

In the following table, the composition of the dry powder charges and the time required to extinguish the fires is given.

Approximate Composition Example Number Time in Standard Additive, Seconds Powder, percent percent 100 0 3 100 0 failed 100 0 tailed 100 0 2% 100 0 3 10 2 90 10 2% 85 15 1% 85 15 1% 75 25 2% 75 25 2 l A commercially available powder containing about 98% sodium blcarbonate and flow enhancing and moisture resisting additives.

! Lithium carbonate.

These tests were conducted in an enclosure adapted to eliminate Wind and to thereby enable the ambient conditions to be duplicated exactly in every instance. From these tests, it will be noted that the powder compositions containing lithium carbonate extinguished the fires from one quarter second to one and one half seconds faster than the charges of substantially 98% sodium bicarbonate. The compositions containing 15% by weight of lithium carbonate acted about twice as fast, respectively, as the 98% sodium bicarbonate charges. This clearly demonstrates the utility and superiority of such compositions in accordance with the present invention.

While the exact manner in which the powder compositions in accordance with the invention function to shorten the time required to extinguish fires has not been determined and it is not desired to attribute the same to any particular theory, it may be that the addition of lithium carbonate within the aforementioned proportions enriches the quality and quantity of evolved gases to produce a more effective smothering or blanketing clfect without impairing the heat absorbing or lowering etfect of the sodium bicarbonate particles'or the solid products of decomposition thereof.

From the foregoing description, it will be seen that the present invention provides an improved dry powder fire extinguishing composition and a method of extinguishing fires therewith in a shorter period of time than heretofore commercially available powders for the same purpose. The powder composition is readily compounded in a simple and economical manner.

As various changes may be made without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it willbe understood that the details and examples hereinbefore set forth are illustrative only, and that the invention as broadly described and claimed is in no way limited thereby.

We claim:

1. A fire extinguishing powder consisting essentially of a finely divided dry mixture of about by weight of sodium bicarbonate, and about 15% by weight of lithium carbonate.

2. The method of extinguishing the fire of burning highly volatile liquids, which method comprises smothering the fire by applying a finely divided dry mixture consisting essentially of about 85% by weight of sodium bicarbonateand about 15% by weight of lithium carbonate.

Gregory: Uses and Applications of Chemicals and Related Materials, pp. 55, 57 (1939), Reinhold Pub. 00., N. Y. 

1. A FIRE EXTINGUISHING POWDER CONSISTING ESSENTIALLY OF A FINELY DIVIDED DRY MIXTURE OF ABOUT 85% BY WEIGHT OF SODIUM BICARBONATE, AND ABOUT 15% BY WEIGHT OF LITHIUM CARBONATE. 